Abstract
Arachidonate epoxidation, which mediates important biological functions in several tissues, is catalyzed by specific cytochrome P450 (CYP) enzymes. Two fatty acid derivatives (2-(2-propynyloxy)-benzenehexanoic acid [PPOH], and N-(methylsulfonyl)-2-(2-propynyloxy)-benzene-hexanamide [MS-PPOH]) are used as general, mechanism- based CYP epoxygenase inactivators, but the effects of these drugs on nearly all CYP isoforms are unknown. Presently, the activity of these compounds on 9 human and 3 rat recombinant CYPs were studied. As expected, PPOH inhibited 5 known epoxygenases (CYPs 2B1, 2B6, 2C6, 2C9, and 2C11 [IC50 = 23 – 161 μM]), but had little or no activity on CYPs typically not considered to be epoxygenases (1A1, 1A2, 1B1, 2A6, 2D6 and 2E1). PPOH was only a very weak inhibitor (IC50 ~ 300 µM) of CYP2C19, an important human expoxygenase. Unexpectedly, MS-PPOH (a metabolically stable congener of PPOH) potently inhibited only two CYP epoxygenases (2C9 and 2C11, IC50 = 11-16 µM), and showed considerably lower activity (IC50 > 90 µM) on all other CYPs tested, including 3 epoxygenases (CYPs 2B1, 2B6, and 2C19). In addition, PPOH and MS-PPOH displayed time- and NADPH-dependent inhibition of CYP2C9 and other epoxygenases. These results support the putative mechanism of action of PPOH and MS-PPOH on recombinant CYPs, and (with one exception) confirm a general epoxygenase inhibitory profile for PPOH. However, the heterogeneity of inhibitory potencies for MS-PPOH on these enzymes suggests caution in the use of this drug as a general epoxygenase inhibitor. These results will facilitate the judicious use of PPOH and MS-PPOH for epoxygenase research.
- Received November 29, 2010.
- Accepted April 1, 2011.
- The American Society for Pharmacology and Experimental Therapeutics